1. Field of the Invention
The present invention relates to an inkjet recording method and inkjet recording apparatus.
2. Description of the Related Art
An inkjet recording method is a method for recording images or the like, in which small liquid drops of ink are jetted and attached to a recording medium such as paper. In the inkjet recording method, an ink composition is generally used which contains various colorants such as dyes and pigments dissolved in water or a mixture of water and organic solvent, and a large quantity of wetting agents consisting of organic solvents having a high boiling point.
In the inkjet recording method, as a recording medium, a recording medium having poor water-absorbing capacity such as commonly used plain paper is sometimes used, in place of an inkjet-dedicated paper excellent in water absorbability. These recording media do not necessarily have an absorbing layer. Accordingly, it is hard for an ink to permeate into the recording medium, so that drying thereof is a time-consuming process.
For example, in a high-speed automatic duplex printing, a one-surface-printed paper is promptly reversed and subjected to the back face printing in an inkjet recording apparatus, which tend to cause a problem that reversal rollers are stained with undried ink.
Meanwhile, when the ink adhesion amount is increased for the purpose of increasing an image density, more time is needed for drying, and image quality tends to degrade due to the feathering of the image.
Accordingly, an inkjet recording method has been demanded which enables to quickly dry ink and produce images of high image density and high quality even when a plain paper is used.
Japanese Patent Application Laid-Open (JP-A) Nos. 2003-534164 and 2004-114691 disclose a method of heating and drying ink during printing process or after the printing process. However, if ink heating is performed during printing process or the like, an inkjet head tends to be deformed by heat, resulting in the degradation of injection stability such as nozzle clogging.
Moreover, if heat enough for drying the ink is applied to the paper, water contained in the paper is also evaporated, to thereby make the paper wavy. In some cases, the paper is even damaged by drying.
JP-A No. 2008-68462 discloses that a preheating process is performed before a printing process to lower the amount of moisture in a paper, so as to shorten the drying time after printing. However, such a heating tends to overdry the fibers of paper and shrinks them, resulting in the waving of the paper. Further, the paper waving becomes more noticeable with partial swelling of the paper fibers due to the absorption of ink, causing excess elevation of humidity in the apparatus.
Furthermore, when the paper waves, an ink ejecting distance directly under the inkjet head varies with the move of the paper, resulting in the occurrence of unevenness in the color image formed by overlapping a plurality of colors.
JP-A No.2003-311940 discloses a technique for forming images by applying a UV curable ink onto a recording medium whose wettability is improved by a plasma treatment.
JP-A No.2000-301711 discloses an inkjet-dedicated paper reformed with plasma and having an ink-receptive layer.
JP-A No.2004-90596 discloses a technique for inkjet recording, in which an ink hardening component was applied onto a recording medium in advance, and ink containing the hardening component is used for the inkjet recording. To apply the hardening component uniformly, the surface of the recording medium is treated with plasma.